Electrical subway



(No Model.)

C. C. GILMAN` ELECTRICAL SUBWAY.

NG. 338,518. Patented Mar. 23, 1886.

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UNITED STATES PATENT OFFICE.

CHARLES CARROLL GILMAN, OF ELDORA, IOVA.

ELECTRICAL SUBWAY.

SFECIFICATION forming part of Letters Patent No. 338,518, dated March 23, 1886.

Application filed October 2G, 1885. Serial No. 180,898. lNo model.)

T @ZZ whom it may concern,.-

Be it known that I, CHARLEs CARROLL GIL- MAN, a citizen ofthe United States, and a resident of Eldora, Hardin county, Iowa, haveinvented a new and usefulImprovement in Electrical Subways or Conduits, of which the following is a specification.

My invention relates to electrical subways for containing wires and cables pertaining to all kinds of electrical service; and it consists in the construction, arrangement, and combination of elements hereinafter described and claimed.

The accompanying drawing is a perspective view of an electrical subway embodying my invention.

In the construction ofthesubway herein described I employ only two materialsterracotta lumber and asphaltum. The former is a porous brick material permeable to nails or screws and workable with saws and common wood-cutting tools. Its weight is less than half of building-brick, though as compared therewith the relative crushing strength is greater. lts cost is less when sawdust is obtainable as a waste, for in the firing process, which eliminates the sawdust, the latter in burning supplies the heat for baking the clay in which it was previously imprisoned by mixing. As indestructible by fire, frost, gases, acids, and age as bricks, its porosity, which is great enough to render it an excellent ltering material, affords notable non-conducting properties of heat, cold, and sound. Its open cellular structure compels thorough impregnation by melted asphalt, unlike brick, affording so deep an anchorage that the two are inseparable under the severest exposure to wet and cold. This exchange of service renders the porous brick material impervious to moisture and augments its natural insulating properties, while it in turn serves as a matrix to uphold in rigid form its otherwise'too pliant tenant.

Asphaltum or mineral pitch is well known and need not be particularly described. It should not, however, be confounded with coaltar or residuums of petroleum distillations, which are worthless for uses here described. In the construction herein set forth it serves not only as a stuffing for the porous brick material, but as the bond wherein the blocks are laid as cement is used in masonry.

In the drawing, A represents blocks of porous terra-cotta or terra-cotta lumber about twelve inches wide, from two to six inches thick, and from one to four feet in length. Said blocks receive a coat of asphaltum at the factory before shipment.

The foundation of' the subway consists of two layers of such blocks so saturated or coated and alternately laid lengthwise and crosswise thatjoints may be broken, as shown. On this foundation the walls of the subway one foot in thickness are erected, the blocks being bonded together by the use of hot melted asphaltum, in which they are for the second time dipped immediately before being placed in position. The foundation between the walls is covered after the erection thereof with a one or two inch layer of asphaltic mastic, B, similar to that in making pavements. Narrow joists C, of saturated terracotta lumber, are laid longitudinally on this layer of mastic, so as to leave spaces in which electric-light or other heavy wires or cables may be placed, said joists and spaces being covered by flooring -blocks D, of saturated terra-cotta lumber, which may be taken up when desired to lay or remove the cables. The supports E for the wires or cables are formed of terra-cotta lumber saturated with asphaltum and are inserted at proper intervals in the walls during the erection thereof, as clearly illustrated in the drawing. Said supports are provided with a series of grooves of sufficient depth and Width to receive and hold in place not only individual wires but large cables.

In order to provide this subway with a strong roof, I use rafters G, (about eight inches deep and four inches wide,) of terra-cotta lumber having an iron core, R, ,cast therein. The outer ends of said rafters are cut away, so as to allow said core to project for a certain distance, and the projecting ends of the core are hooked into the eyes T of an iron or steel tie-rod, S, resting in grooves on top of the outer walls, this combination of iron cores and tie-rods affording substantially a trussed roof. The outer surface of the rafters is covered with a layer, I, of asphalt mastic an inch IOO an insulator. In this respectit possesses great lo advantages over metal pipes usually employed.

Lateral branches or conduits can'be connccted with the subway at any place and at any time, since the materials of which the walls are constructed can be bored and sawed 15 with ordinary wood-working tools, so that an opening of the exact'size can be quickly made and as quickly repaired at any desired place.

Having thus described my invention, what I claim,' and desire to secure by Letters Pat- 2o ent, is-

1. An electrical subway provided with a floor of asphalt mastic laid on a foundation of terracotta lumber, narrow joists ofasphaltum, coated or saturated terra-cotta lumber properly spaced laid on said floor, and a covering 25 of iiooring-blocks of the same material as said joists, whereby insulated supports for cables are provided, substantially as described.

2. An electrical subway provided with a roof constructed of rafters of asphaltum7 coat- 3o ed or saturated terra-cotta lumber strengthened by iron cores cast therein, combined with a tie-rod connecting said cores, forming substantially a trussed roof, substantially as described. 3 5

3. 'An electrical subway provided with 'a roof constructed of rafters of asphaltum, covered or saturated terra-cotta lumber strengthened by iron cores cast therein, combined with a tie-rod provided with eyes engaging 4o vthe ends 4of said iron cores, forming substantially atrussed roof, substantially as described. In testimony whereof I have signed -my name in the presence of two witnesses.

CHARLES CARROLL GILMAN. Witnesses:

SAML. G. SLoAN, EDWIN S. J AGGARD.' 

